1. Field of the Invention
The present invention relates to a television camera/recorder, which is generally known as Camcorder--consisting of a television camera and a VTR, and a system for transmitting signals reproduced by the television camera/recorder.
2. Description of the Related Art
Recently, the use of a television camera/recorder integrally comprising a domestic television camera and a VTR has become prevalent. In the television camera/recorder, video signals produced by the television camera are recorded by the VTR on a magnetic tape, and the VTR reproduces the video signals from the magnetic tape and transmits the reproduced video signals to a monitoring receiver or a television receiver. Then, the monitoring receiver or the television receiver displays pictures represented by the video signals on its display. In the following description, a receiver provided with a video signal input terminal and an audio signal input terminal will be called a monitoring receiver, and a receiver not provided with any video signal input terminal and any audio signal input terminal and provided with only an antenna terminal will be called a television receiver to simplify the description.
Referring to FIG. 8, when displaying a picture on and reproducing sounds by a monitoring receiver 1 provided with a video signal I/O terminal 1v and an audio signal I/O terminals 1a, the video signal I/O terminal 11v and the audio signal I/O terminal 11a having two jacks for two-channel stereo audio signals of a conventional television camera/recorder 10 are connected respectively to the video signal I/O terminal 1v and the audio signal I/O terminal 1a by a 13-pin cord CB. When an external microphone is used in combination with the television camera/recorder 10, a dc supply voltage is applied to the external microphone through dc voltage output terminal 11d. The dc voltage that appears at the dc voltage output terminal can be used as an antenna changing signal when a RF converter is used, which will be described later.
FIG. 9 shows a known system comprising a television camera/recorder 10 and an adapter 20. Video signals reproduced by the television camera/recorder 10 can be supplied to a monitoring receiver 1 simply by placing the television camera/recorder on the adapter 20 and setting the television camera/recorder 10 to a reproducing mode to display pictures represented by the reproduced video signals on the monitoring receiver 1. As shown in FIG. 9, the television camera/recorder 10 is provided on its bottom wall with a video signal output electrode 12v, audio signal output electrodes 12a, a dc voltage output electrode 12d, which corresponds to the dc voltage output terminal 11d, a video signal grounding electrode Ev, an audio signal grounding electrode Ea, and a dc voltage grounding electrode Ed. The signal system and the power system of the television camera/recorder are grounded individually. The conductors 12v, 12a, 12d, Ev, Ea and Ed are formed of a conductive metal.
The adapter 20 is provided on its upper wall on which the television camera/recorder 10 is placed with a video signal input electrode 21v, audio input electrodes 21a, a dc voltage input electrode 21d, and grounding electrodes with which the output electrodes 12v, 12a and 12d, and the grounding electrodes Ev, Ea and Ed come into contact when the television camera/recorder 10 is placed on the adapter 20. Output terminals (jacks) 22v, 22a and 22d to be connected through amplifiers, not shown, respectively to the electrodes 21v, 21a and 21d are arranged on the side wall of the adapter 20.
The output terminals 22v and 22a are connected constantly to the input terminals 1v and 1a of a monitoring receiver 1, respectively, by an AV cord. Consequently, the output electrodes 12v and 12a of the television camera/recorder 10 are connected electrically through the input electrodes 21v and 21a and the output terminals 22v and 22a of the adapter 20 to the video signal input terminal 1v and the audio signal input terminals 1a of the monitoring receiver 1 simply by placing the television camera/recorder 10 on the adapter 20 to apply video signals and audio signals reproduced by the television camera/recorder 10 to the monitoring receiver 1, and then the monitoring receiver 1 reproduces images and sounds.
When reproducing images on a television receiver provided with neither video signal input terminals nor audio signal input terminals, signals reproduced by the television camera/recorder 10 are converted into signals of an idle channel for television broadcasting, i.e., carrier television signals by a separate RF converter and the carrier television signals are transmitted to the antenna terminal of the television receiver through a circuit as shown in FIG. 9.
Referring to FIG. 10 and 11, a television receiver 2 is provided with a receiving antenna 3 for receiving television signals. A RF converter 30C is connected to an antenna switch 30SW by a cord 38. The RF converter 30C is provided with a video signal input terminal (plug) 31v, audio signal input terminals (plug) 31aR and 31aL, which are denoted inclusively by 31a, and a dc power input terminal (2-pole miniplug) 31d. The RF converter 30C is joined to the television camera/recorder 10 with its video signal input terminal 31v, audio signal input terminals 31a and the dc power input terminal 31d connected respectively to the video signal I/O terminal 11v, the audio signal I/O terminals 11a and the dc power output terminal 11d (such as a 2-pole minijack) of the television camera/recorder 10, Dc power is supplied from the television camera/recorder 10 to the RF converter 30C through the dc I/O terminal 11d of the television camera/recorder 10 and the dc input terminal 31d of the RF converter 30C.
Video signals Sv provided by a video signal processing circuit 14v included in the television camera/recorder 10 and audio signals Sa provided by an audio signal processing circuit 14a included in the television camera/recorder 10 are transmitted respectively through I/O transfer switches 13v and 13a to modulators 33v and 33a included in the conversion circuit 32 of the RF converter 30C. The modulator 33v of the RF converter 30C converts the output of an oscillator 34 of a predetermined channel for amplitude modulation to provide a video carrier signal Srv, and another modulator 33a modulates the output of an oscillator, not shown, of a suitable frequency for frequency modulation. The output of the modulator 33a is converted into a carrier audio signal Sra by beat-up or the like. Then, the video signals Sv and the audio signals Sa are converted into carrier television signals Srf of an idle television channel in a VHF band or a UHF band.
Resonators 36a and 36b respectively corresponding to two idle channels A and B which are not used in an area in which the RF converter 30C is used are connected through a transfer switch 35 to the oscillator 34. Either the resonator 36a or the resonator 36b is selected by the transfer switch 35 to select either the idle channel A or the idle channel B. The carrier television signals Srf provided by the conversion circuit 32 are transmitted through a suitable band-pass filter 37 to an electronic or mechanical switch 39 included in the antenna switch 30SW. The carrier television signals Srf are transmitted through the movable contact and the r-side fixed contact of the switch 39 to the antenna terminal 2a of a television receiver 2. Then, the television receiver 2 displays pictures represented by the reproduced video signals on its screen and generates sounds represented by the reproduced audio signals by its loudspeakers.
The receiving antenna 3 is connected to the a-side fixed contact of the transfer switch 39. When the RF converter 30C is used, the movable contact of the switch 39 is connected to the r-side fixed contact by dc power supplied through the output terminal 11d and the dc power input terminal 31d of the RF converter 30C by a power control circuit 15 included in the television camera/recorder 10 to avoid interference in television receivers in the neighborhood of the RF converter 30C. The power control circuit 15 is provided with a current intensity detecting means, not shown. When the current intensity detecting means detects the flow of an excessively high current through the dc power output terminal 11d due to short-circuiting or the like, the power control circuit 15 decreases the output voltage to maintain the intensity of the current flowing through the dc power output terminal 11d within a predetermined output power range.
Thus, four connecting systems are necessary for connecting the RF converter 30C and the television camera/recorder 10 for video signals, stereophonic signals including right-channel audio signals and left-channel audio signals, and dc power. At least three connecting systems are necessary even if monophonic signals are used.
When a high-performance external microphone, such as an electret microphone, is used to record sounds in combination with the television camera/recorder 10 when televising a scene by the television camera/recorder 15, power is supplied to the external microphone through the dc power output terminal 11d.
When the adapter 20 is provided with a dc voltage output electrode 21d and a dc voltage output terminal on its upper wall and side wall, the RF converter 30C can be connected to the adapter 20 to enable the image of the scene formed by the television camera/recorder 10 to be displayed in corresponding pictures on the television receiver 2 by the foregoing very simple procedure.
As mentioned above, when the conventional television camera/recorder 10 is not used for televising a scene or reproducing recorded signals, the transfer switch 13v and 13a are set so as to transmit signals reproduced by an ordinary VTR or video and audio signals provided by a TV tuner through the video signal I/O terminal 11v and the audio signal I/O terminals 11a to the video signal processing circuit 14v and the audio signal processing circuit 14a to record the signals reproduced by the ordinary VTR or the video and audio signals provided by the TV tuner in the same recording manner as that in which an ordinary VTR records signals.
The RF converter 30C separate from the television camera/recorder 10 is connected to the television camera/recorder 10 by plugging the video signal input terminal 31v, the audio signal input terminals 31a and the dc power input terminal 31d, which are formed in plugs, respectively in the video signal I/O terminal 11v, the audio signal I/O terminals 11a and the dc power output terminal 11d, which are formed in jacks. Therefore, when the television camera/recorder 10 and the RF converter 30C are thus combined, the video signal I/O terminal 11v and the audio signal I/O terminals 11a are occupied and hence the television camera/recorder is unable to function as an individual VTR. Furthermore, since the jacks of the television camera/recorder 10 are inserted in the jacks of the RF converter 30C when combining the television camera/recorder 10 and the RF converter 30C, it is not necessarily easy to join the RF converter 30C to, and to separate the same from, the television camera/recorder 10, which deteriorates the reliability of the electrical connection of the plugs and the jacks.